Animal husbandry on the Mongolian Plateau is a dynamic human–natural system characterized by complex relationships with the grassland ecosystem. Sustainable use of the plateau's grassland depends on the ability of herders and decision makers to adjust the grazing pattern to adapt to extreme climate events and socioeconomic conditions. Unfortunately, the system's responses and adaptation to these changes are unclear. However, simultaneously studying the natural and human factors will improve the understanding of the adaptations of grazing and the grassland ecosystem. The goal of this comparative study was to reveal the relationship between livestock management and government policy, natural conditions, and socioeconomic conditions near the border between Mongolia and China's Inner Mongolia Autonomous Region. In this study, we used spatial and statistical data in the analysis of the dynamics of livestock. (1) China implemented a livestock reduction policy, whereas Mongolia increased livestock through privatization of livestock and the development of an economic market. In addition, Mongolian herders raised more goats. (2) The livestock population was significantly positively correlated with vegetation cover (represented by the normalized difference vegetation index) during years of severe weather in both Inner Mongolia and Mongolia. (3) The goat population was influenced significantly by the export amount in Mongolia, but by the return on investment in Inner Mongolia. (4) The livestock population was only weakly related to the rural population and the number of herder households. Our findings provide a basis for improving grassland and animal management strategies in both countries. Co-management of the grassland and livestock by herders and the government will be needed to balance herder livelihoods with the grassland ecosystem.